7.12.2 Using Symbolic Links with Disk Data Objects

The performance of a MySQL Cluster that uses Disk Data storage
can be greatly improved by separating data node file systems
from undo log files and tablespace data files and placing these
on different disks. Previous to MySQL Cluster NDB 6.2.17, MySQL
Cluster NDB 6.3.22, and MySQL Cluster NDB 6.4.3, there was no
direct support for this in MySQL Cluster, but it was possible to
achieve this separation using symbolic links as described in
this section.

Each data node in the cluster creates a file system in the
directory named
ndb_node_id_fs
under the data node's
DataDir as defined in
the config.ini file. In this example, we
assume that each data node host has 3 disks, aliased as
/data0, /data1, and
/data2, and that the cluster's
config.ini includes the following:

[ndbd default]
DataDir= /data0

Our objective is to place all Disk Data log files in
/data1, and all Disk Data data files in
/data2, on each data node host.

Note

In this example, we assume that the cluster's data node
hosts are all using Linux operating systems. For other
platforms, you may need to substitute you operating
system's commands for those shown here.

To accomplish this, perform the following steps:

Under the data node file system create symbolic links
pointing to the other drives:

If you are running multiple data nodes on one host, you must
take care to avoid having them try to use the same space for
Disk Data files. You can make this easier by creating a
symbolic link in each data node file system. Suppose you are
using /data0 for both data node file
systems, but you wish to have the Disk Data files for both
nodes on /data1. In this case, you can
do something similar to what is shown here: